Vanadium nitride film, and member coated with vanadium nitride film and method for manufacturing the same

ABSTRACT

In a vanadium nitride film formed on a surface of a base material, a ratio V [at %]/N [at %] between a vanadium element concentration and a nitrogen element concentration in the film is 1.08 or more and a chlorine element concentration in the film is 1 at % or more and 5 at % or less.

The present application is a Divisional of U.S. application Ser. No.16/319,604, filed Jan. 22, 2019, which is a U.S. National stage ofInternational Patent Application No. PCT/JP2017/027222, filed Jul. 27,2017, which claims priority to Japanese Application No. 2016-146948,filed Jul. 27, 2016. The disclosures of each of the applications listedabove are incorporated by reference herein in their entireties.

TECHNICAL FIELD

The present invention relates to a vanadium nitride film formed on asurface of a base material, and a coated member coated with the vanadiumnitride film and a method for manufacturing the same.

BACKGROUND ART

Conventionally, the formation of a vanadium nitride film high in filmhardness and rich in lubricity has been performed as a hard coatingtreatment on the surface of a die of press forming, a cutting tool, agear cutting tool, a forging tool and so on.

As such a method for manufacturing the conventional vanadium nitridefilm, a method for forming a vanadium nitride film by the arc ionplating method is disclosed in Patent Document 1. Patent Document 1discloses a vanadium nitride film having a Vickers hardness HV of about2000. Further, Patent Document 2 also discloses a method for forming avanadium nitride film by the ion plating method. Patent Document 2discloses a vanadium nitride film having a Vickers hardness HV of about2300.

PRIOR ART DOCUMENT Patent Document

-   Patent Document 1: Japanese Laid-open Patent Publication No.    2002-371352-   Patent Document 2: Japanese Laid-open Patent Publication No.    2005-46975

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Normally, a harder coating is richer in abrasion resistance, but thehardness of the conventional vanadium nitride film has been about HV2300. Accordingly, it has been required to form a vanadium nitride filmhaving higher hardness for improvement of abrasion resistance.

A vanadium nitride film and a member coated with a vanadium nitride filmaccording to the present invention have been made in consideration ofthe above circumstances and an object thereof is to improve the hardnessof the vanadium nitride film.

Besides, as the conventional film formation method of the vanadiumnitride film, a physical vapor deposition method represented by the ionplating has been used, and therefore there is a need to take measures tothe film formation apparatus such as provision of a rotation mechanismat a work table in the film formation processing on a complicated shapearticle such as a die because of poor throwing power of evaporatingparticles. Therefore, for the conventional film formation method of thevanadium nitride film, a film formation apparatus of specialspecifications for the film formation for the complicated shape articleneeds to be prepared, bringing about a problem of an increase in costaccompanying the introduction of the film formation apparatus. On theother hand, as the film formation method excellent in throwing power,the plasma chemical vapor deposition method is known. However, there isnot any known method for manufacturing a vanadium nitride film using theplasma chemical vapor deposition method, and it has been completelyunclear whether the plasma chemical vapor deposition method can improvethe hardness of the vanadium nitride film and, in the first place,whether the plasma chemical vapor deposition method can be used formanufacture of the vanadium nitride film as a hard coating.

A method for manufacturing a member coated with a vanadium nitride filmaccording to the present invention has been made in consideration of theproblem and the aforementioned problems regarding the abrasionresistance of the vanadium nitride film, and an object thereof is toimprove the hardness of the vanadium nitride film and to suppress thecost accompanying the introduction of the film formation apparatus.

Means for Solving the Problems

The present inventors have focused attention on the ratio between avanadium element concentration [at %] and a nitrogen elementconcentration [at %] in the vanadium nitride film, and have found thatwhen the ratio is 1.08 or more, the hardness of the vanadium nitridefilm improves. More specifically, the present invention solving theabove problem is a vanadium nitride film formed on a surface of a basematerial, wherein a ratio V [at %]/N [at %] between a vanadium elementconcentration and a nitrogen element concentration in the film is 1.08or more and a chlorine element concentration in the film is 1 at % ormore and 5 at % or less. Note that the “vanadium nitride film” means afilm composed of a compound containing vanadium and nitrogen as maincomponents, and an example thereof is a film of a compound expressed bya chemical formula such as VN, V₂N, VN_(0.81).

The present invention according to another aspect is a member coatedwith a vanadium nitride film, wherein a vanadium nitride film having aratio V [at %]/N [at %] between a vanadium element concentration and anitrogen element concentration of 1.08 or more and a chlorine elementconcentration of 1 at % or more and 5 at % or less is formed on asurface of a base material.

The present invention according to still another aspect is a method formanufacturing a member coated with a vanadium nitride film, the methodincluding: supplying a raw material gas containing a nitrogen sourcegas, a vanadium chloride gas, and a hydrogen gas in forming the vanadiumnitride film on a surface of a base material; and forming a vanadiumnitride film having a ratio V [at %]/N [at %] between a vanadium elementconcentration and a nitrogen element concentration of 1.08 or more and achlorine element concentration of 1 at % or more and 5 at % or less onthe surface of the base material by a plasma chemical vapor depositionmethod.

Effect of the Invention

According to the present invention, it is possible to obtain a vanadiumnitride film improved in hardness as compared with the conventional one.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A schematic view illustrating a configuration of a film formationapparatus for a vanadium nitride film according to an embodiment of thepresent invention.

FIG. 2 A schematic view illustrating a film structure of a member coatedwith a vanadium nitride film according to another embodiment of thepresent invention.

FIG. 3 A schematic view illustrating a film structure of a member coatedwith a vanadium nitride film according to another embodiment of thepresent invention.

FIG. 4 A cross-sectional image of a test piece in Example 1 observedunder a metallurgical microscope.

MODES FOR CARRYING OUT INVENTION

Hereinafter, an embodiment of the present invention will be explainedreferring to the drawings. Note that in this specification and thedrawings, the same codes are given to components having substantiallythe same functional configurations to omit duplicated explanation.

In this embodiment, a plasma chemical vapor deposition method (aso-called plasma CVD method) is used to form a vanadium nitride filmcomposed of a compound containing, as main components, vanadium andnitrogen on the surface of a base material. More specifically, avanadium nitride film is formed which has a ratio between a vanadiumelement concentration [at %] and a nitrogen element concentration [at %]in the film of 1.08 or more. Note that though die steel such as SKD11,other tool steel or the like is used as the base material, but the basematerial is not limited to these materials. Any material may be adoptedas the base material as long as it requires a hard coating treatmentaccording to the strength inherent to the material and usage and so on.

In this embodiment, as a film formation apparatus for forming a vanadiumnitride film, a plasma processing apparatus 10 as illustrated in FIG. 1is used. The plasma processing apparatus 10 includes a chamber 11 intowhich a base material 2 is carried in, an anode 12 and a cathode 13, anda pulse power supply 14. A gas supply pipe 15 from which a raw materialgas is supplied is connected to an upper part of the chamber 11, and agas exhaust pipe 16 which exhausts gas in the chamber is connected to alower part of the chamber 11. On the downstream side of the gas exhaustpipe 16, a vacuum pump (not illustrated) is provided. The cathode 13also has a role as a support table which supports the base material 2,and the base material 2 carried in the chamber is mounted on thecathode. Further, inside the chamber 11, a heater (not illustrated) isprovided, so that the heater adjusts an atmospheric temperature in thechamber and thereby adjusts the temperature of the base material 2.

Note that the configuration of the plasma processing apparatus 10 is notlimited to the one explained in this embodiment. For example, ahigh-frequency power source may be used in place of the pulse powersupply 14, or a shower head which supplies the raw material gas may beprovided and used as the anode 12. Further, the base material 2 may beheated only with glow current without providing the heater. In short,the plasma processing apparatus 10 only needs to have a structurecapable of converting the raw material gas supplied in the chamber intoplasma and form the vanadium nitride film 3 on the base material 2 so asto manufacture a member coated with a vanadium nitride film 1.

Next, a method for manufacturing the member coated with a vanadiumnitride film 1 will be explained.

<Film Formation Processing Preparation>

First of all, the base material 2 is carried into the chamber 11 and thebase material 2 is set at a predetermined position. Thereafter,evacuation is performed so that the pressure in the chamber becomes, forexample, 10 Pa or less. In this event, the temperature in the chamber isabout room temperature, Subsequently, the heater is operated to performa baking treatment on the base material 2. Thereafter, the heater isturned off once, and the plasma processing apparatus 10 is let stand fora predetermined time.

<Heating Step>

Next, a small amount of hydrogen gas is supplied into the chamber, andthe heater is operated again. At this heating process, the temperatureof the base material 2 is raised up to near a plasma processingtemperature. The pressure in the chamber is maintained, for example, atabout 100 Pa. Note that the temperature of the base material 2 maybecome a factor that affects the amount of vanadium in the film, andtherefore one example of a method in adjusting the amount of vanadium inthe film can be an adjustment of the temperature of the base material 2.Increasing the temperature of the base material 2 enables an increase inthe amount of vanadium in the film.

<Plasma Processing Step>

Subsequently, film formation processing of the vanadium nitride film 3using the plasma CVD method is performed. In this embodiment, thehydrogen gas is converted into plasma prior to the film formationprocessing of the vanadium nitride film 3. Specifically, the pulse powersupply 14 is operated in a state where the hydrogen gas supplied at theheating step is continuously supplied. Hydrogen radicals generated inthis manner reduce an oxidation film on the surface of the base materialand clean the surface of the base material 2 before the film formation.Note that the voltage, the frequency, the Duty ratio and so on of thepulse power supply 14 are appropriately set so as to convert the gassupplied in the chamber into plasma.

After converting the hydrogen gas into plasma, a nitrogen gas and anargon gas are further supplied into the chamber into which the hydrogengas is being supplied. This generates plasma of the hydrogen gas, thenitrogen gas, and the argon gas and thereby can stabilize the glowdischarge before the formation of the vanadium nitride film.

Thereafter, as a vanadium source gas, a vanadium chloride gas is furthersupplied into the chamber. This makes a state where the nitrogen gas,the vanadium chloride gas, the hydrogen gas, and the argon gas as theraw material gas for forming the vanadium nitride film 3 are suppliedinto the chamber. The ratio of partial pressures of the nitrogen gas,the vanadium chloride gas, the hydrogen gas, and the argon gas is set,for example, to 9-10:0.9-1.2:35-50:0.5-5. Further, the pressure in thechamber is set, for example, to 50 Pa or more and 200 Pa or less. Notethat the nitrogen source gas for forming the vanadium nitride film 3 isnot limited to the nitrogen gas but may be an ammonia gas. Further, asthe vanadium source gas for forming the vanadium nitride film 3, thevanadium chloride gas is used which is likely to decompose. For example,a vanadium tetrachloride gas (VCl₄) or a vanadium trichloride oxide(VOCl₃) gas is used. It is particularly preferable to use the vanadiumtetrachloride gas (VCl₄) because the number of elements constituting thegas is smaller and removal of impurities in the vanadium nitride filmbecomes easier. Further, the vanadium tetrachloride gas (VCl₄) ispreferable also in terms of being easily available, being liquid at roomtemperature, and being easy supply as a gas.

When the vanadium chloride gas is supplied into the chamber, thevanadium chloride gas is converted into plasma between the electrodes.The vanadium gas and the nitrogen gas converted into plasma between theelectrodes adhere to the base material 2, whereby the vanadium nitridefilm 3 is formed on the surface of the base material 2. Note that theatmospheric temperature in the chamber in the film formation processingof the vanadium nitride film 3 is preferably 450° C. or higher and 600°C. or lower. The voltage in the film formation processing is preferably700 V or higher and 1800 V or lower. Further, since a glow current valuein plasma generation influences the nitrogen amount in the film,increasing the glow current value enables an increase of the nitrogenamount in the film.

Though the hardness of the vanadium nitride film 3 is differentdepending on the processing conditions in the film formation processing,the vanadium nitride film 3 having a ratio (V [at %]/N [at %]) of thenitrogen element concentration to the vanadium element concentration inthe film becomes 1.08 or more is formed in this embodiment. Note that inthe following explanation, the ratio (V [at %]/N [at %]) between thevanadium element concentration and the nitrogen element concentration inthe film is expressed as a “VN concentration ratio” in some cases.

As illustrated in later-explained examples, the vanadium nitride film 3having a VN concentration ratio of 1.08 or more has such a hardness thata Vickers hardness HV converted based on Martens hardness obtained by anano-indentation method is 2400 or more. In short, the vanadium nitridefilm 3 is formed with the plasma processing conditions appropriately setso that the VN concentration ratio becomes 1.08 or more using the plasmaCVD method, whereby the vanadium nitride film 3 having a hardness whichcannot be obtained by the ion-plating method as in the prior art can beobtained. Thus, the member coated with a vanadium nitride film 1improved in abrasion resistance as compared with the prior art can beobtained. Note that the VN concentration ratio can be controlled bygradually changing, during the film formation processing, at least oneof parameters influencing the VN concentration ratio, such as thepressure and the atmospheric temperature in the chamber, the hydrogengas partial pressure, the nitrogen gas partial pressure, the glowcurrent value and so on in the film formation processing.

The VN concentration ratio is preferably 1.10 or more and morepreferably 1.30 or more. This can further improve the hardness of thevanadium nitride film. Further, the upper limit of the VN concentrationratio is preferably 2.5, more preferably 2.0 or less, and furthermorepreferably 1.85 or less. The total of the vanadium element concentrationand the nitrogen element concentration of the vanadium nitride film ispreferably 90 at % or more. Further, the upper limit of the total of thevanadium element concentration and the nitrogen element concentration ofthe vanadium nitride film is preferably 99 at %. The elementconcentration of vanadium of the vanadium nitride film is preferably49.5 at % or more, more preferably 50 at % or more, and furthermorepreferably 53 at % or more. Further, the upper limit of the elementconcentration of vanadium of the vanadium nitride film is preferably 70at %. The film thickness of the vanadium nitride film is appropriatelyset according to a product being a film formation object, and apreferable film thickness is 0.5 μm or more and 10 μm or less. A furtherpreferable lower limit of the film thickness is 2 μm.

In the film formation method according to this embodiment, the vanadiumchloride gas is used as the vanadium source gas in the film formation ofthe vanadium nitride film, and therefore chlorine is necessarilycontained in the vanadium nitride film, and the lower limit of thechlorine element concentration of the vanadium nitride film ispreferably 1 at %. A preferable lower limit of the chlorine elementconcentration in the film is 1.5 at % and a furthermore preferable lowerlimit is 2 at %. On the other hand, if chlorine in the film exceeds 5 at%, the vanadium nitride film may have deliquescence and the film maydisintegrate under air atmosphere. Therefore, in the film formation ofthe vanadium nitride film according to this embodiment, the vanadiumnitride film is formed so that the chlorine concentration in the filmbecomes 1 at % or more and 5 at % or less by appropriately setting theplasma processing conditions. In contrast to this, in the film formationmethod of the vanadium nitride film by the conventional ion platingmethod, metallic vanadium is used as the vanadium source, so thatchlorine is not contained in the film.

Note that the hydrogen gas contained in the raw material gas is likelyto combine with chlorine, so that when the hydrogen gas is contained asthe raw material gas as in this embodiment, chlorine generated from thevanadium chloride gas combines with hydrogen and becomes likely to bedischarged to the outside the system, enabling suppression of mixture ofchlorine into the film. of the vanadium nitride film 3. As a result, adecrease in hardness of the film due to mixture of a large amount ofchlorine into the film can be suppressed. The flow rate of the hydrogengas is preferably 25 times or more to the flow rate of the vanadiumchloride gas. Further, though the argon gas is contained in the rawmaterial gas in this embodiment, supply of the argon gas is notessential. Argon ions of the argon gas ionize other molecules andthereby contribute to stabilization of plasma and improvement in iondensity, and therefore the argon gas is preferably supplied as needed.

Further, when the plasma CVD method is used in the film formationprocessing of the vanadium nitride film 3 as in this embodiment, anapparatus equivalent to the film formation apparatus used in the filmformation processing of other than a complicated shape article can beused also in the film formation processing for the complicated shapearticle. In other words, a film formation apparatus of specialspecifications for the film formation for the complicated shape articlebecomes unnecessary, thus enabling reduction of cost accompanying theintroduction of the film formation apparatus. Further, even when both ofthe film formation apparatus of special specifications and the filmformation apparatus of ordinary specifications are necessary in theconventional film formation method, the film formation apparatus ofspecial specifications becomes unnecessary according to the filmformation method of this embodiment, thus enabling reduction in thenumber of film formation apparatuses to be installed in a factory. Thiscan increase the degree of freedom of the facility layout in thefactory.

Further, the vanadium nitride film 3 in this embodiment is a film havinga Vickers hardness HV of 2400 or more and a complex elastic modulus of400 GPa or less. Normally, the hardness and the complex elastic modulusare in a proportional relation, and the complex elastic modulusgenerally increases with an increase in hardness. However, the vanadiumnitride film 3 in this embodiment has a complex elastic modulussuppressed to 400 GPa or less though a Vickers hardness HV reaches 2400or more. This is a low complex elastic modulus even compared with thefilm having the same level of hardness and means that an elasticallydeformed region is wide. More specifically, the vanadium nitride film 3in this embodiment has high abrasion resistance relative to the filmhaving the same level of hardness. Accordingly, the member coated with avanadium nitride film 1 in this embodiment coated with such a vanadiumnitride film 3 is a member achieving both the hardness and the complexelastic modulus at high levels and has more excellent abrasionresistance than the conventional one. Note that in the case where the VNconcentration ratio is in a range of 1.30 to 1.85, both of a hardness ofHV of 2900 or more and a complex elastic modulus of 350 GPa or less canbe achieved.

While the embodiment of the present invention has been described, thepresent invention is not limited to the example. It should be understoodthat various change examples and modification examples are readilyapparent to those skilled in the art within the technical spirit as setforth in claims, and those should also be covered by the technical scopeof the present invention.

For example, though the vanadium nitride film 3 is formed on the surfaceof the base material 2 in the above embodiment, a vanadium nitride film4 having a VN concentration ratio in the film of 0.70 or more and lessthan 1.08 may be formed on the surface of the base material 2 and avanadium nitride film 3 having a VN concentration ratio of 1.08 or moremay be formed on the surface of the vanadium nitride film 4 asillustrated in FIG. 2. The vanadium nitride film 4 having a VNconcentration ratio of 0.70 or more and less than 1.08 is a film softerthan the vanadium nitride film 3 having a VN concentration ratio of 1.08or more but is a film harder than the base material 2. The vanadiumnitride film 4 having a VN concentration ratio of 0.70 or more and lessthan 1.08 formed as described above can suppress a rapid change inhardness between the vanadium nitride film 3 having a VN concentrationratio of 1.08 or more and the base material 2. This decreases thedifference between the films and thereby can improve the adhesionbetween the films. In this specification, the vanadium nitride film 4having a VN concentration ratio of 0.70 or more and less than 1.08 iscalled a “buffer film”.

Further, as another embodiment, a concentration gradient film 5 whichgradually increases in VN concentration ratio in a range of 0.70 to 1.08from the base material side toward the vanadium nitride film side may beformed between the base material 2 and the vanadium nitride film 3. Alsoin the case where the concentration gradient film 5 is formed, theadhesion at the interface between the films increases to make thevanadium nitride film 3 hard to peel off from the base material 2. Notethat for formation of the concentration gradient film 5 of vanadium andnitrogen on the surface of the base material 2, it is only necessary togradually change, during the film formation processing, at least one ofthe parameters influencing the VN concentration ratio, such as thepressure and the atmospheric temperature in the chamber, the hydrogengas partial pressure, the nitrogen gas partial pressure, the glowcurrent value and so on in the film formation processing.

EXAMPLES

The vanadium nitride film (VN film) was formed on the surface of thebase material using the plasma CVD method, and the hardness of thevanadium nitride film was evaluated.

As the base material on which the vanadium nitride film was formed, theone was used which was obtained by performing quenching and temperingtreatments on a round bar of ϕ22 composed of SKD11 being one kind of thedie steel and then cutting the round bar at an interval of 6 to 7 mm,and performing mirror polishing on the surface of each cut member. Notethat the vanadium nitride film was formed on a surface on the sidesubjected to the mirror polishing of the base material. The filmformation apparatus having the structure illustrated in FIG. 1 was used,and the pulse power supply was used as the power supply. A series ofprocessing conditions until the film formation processing are listed infollowing Table 1.

TABLE 1 PROCESSING CONDITIONS (EXAMPLE 1) STEP HEATER H₂ H₂ + N₂ +Ar VNFILM EVACUATION BAKING COOLING TEMPERATURE UP PLASMA PLASMA FORMATIONHEATER SETTING HEATER OFF 200 HEATER OFF 485 485 485 485 TEMPERATURE (°C.) PRESSURE (Pa) DOWN TO 10 Pa NOT NOT 100 100 58 58 CONTROLLEDCONTROLLED H₂ FLOW RATE (ml/min) 0 5 5 100 100 200 200 N₂ FLOW RATE(ml/min) 0 0 0 0 0 50 50 VCl₄ FLOW RATE (sccm) 0 0 0 0 0 0 5.1 Ar FLOWRATE (ml/min) 0 0 0 0 0 5 5 VOLTAGE OF PULSE 0 0 0 0 800 1100 1500 POWERSUPPLY (V) FREQUENCY OF PULSE 0 0 0 0 25 25 25 POWER SUPPLY (kHz) DUTYRATIO (%) 0 0 0 0 30 30 30 OUTPUT FORM 0 0 0 0 UNIPOLAR UNIPOLARUNIPOLAR PROCESSING TIME (min) 30 10 30 30 20 20 180

Concrete explanation is as follows.

<Film Formation Processing Preparation>

First of all, the base material is set in the chamber of the filmformation apparatus, the chamber is evacuated for 30 minutes to reducethe pressure in the chamber down to 10 Pa or less. In this event, theheater is not operated. Note that the heater is provided inside thechamber, and the atmospheric temperature in the chamber is beingmeasured by a sheathed thermocouple. Subsequently, the settingtemperature of the heater is set to 200° C. and a baking treatment isperformed on the base material for 10 minutes. Thereafter, the heater isturned off, and the film formation apparatus is let stand for 30 minutesto cool the inside of the chamber.

<Heating Step>

Next, the hydrogen gas is supplied at a flow rate of 100 ml/min into thechamber and the exhaust rate is adjusted to set the pressure in thechamber to 100 Pa. Then, the setting temperature of the heater is set to485° C. and the base material is heated for 30 minutes. This heatingstep raises the temperature of the base material up to near the plasmaprocessing temperature.

<Plasma Processing Step>

Next, the pulse power supply is operated at a voltage: 800 V, afrequency: 25 kHz, a Duty ratio: 30%, and a unipolar output form. Thisconverts the hydrogen gas into plasma between the electrodes in thechamber. Thereafter, the flow rate of the hydrogen gas is increased to200 ml/min and the nitrogen gas and the argon gas are supplied into thechamber. Then, the voltage of the pulse power supply is raised to 1100V. This makes the hydrogen gas, the nitrogen gas, and the argon gas intoa plasma state between the electrodes. Note that the flow rate of thenitrogen gas in this event is set to 50 ml/min and the flow rate of theargon gas is set to 5 nil/min. Further, the exhaust rate is adjusted toset the pressure in the chamber to 58 Pa.

Subsequently, the vanadium tetrachloride gas is supplied into thechamber and the voltage of the pulse power supply is raised to 1500 VThis decomposes the vanadium tetrachloride gas into vanadium andchlorine. Then, vanadium and nitrogen converted into plasma adhere tothe base material, whereby a vanadium nitride film is formed on thesurface of the base material. This state is maintained for 180 minutes.

Through the above steps, a test piece in which the vanadium nitride filmis formed on the surface of the base material is obtained. In thisexample, other than this test piece, a plurality of test pieces inExamples 2 to 5 and Comparative Examples 1 to 2 which were produced withthe processing conditions at start of the supply of the vanadiumtetrachloride gas into the chamber, namely, the processing conditions inthe film formation of the vanadium nitride film (film formationprocessing conditions) changed, were prepared. The film formationprocessing conditions are listed in following Table 2. Note that theprocessing conditions from the supply of the vanadium tetrachloride gasinto the chamber to the start of the film formation of the vanadiumnitride film in Examples and Comparative Examples are the same as theprocessing conditions listed in above Table 1. Further, the processingconditions in above Table 1 are conditions for manufacturing the testpiece in Example 1 listed in following Table 2.

TABLE 2 EXAMPLE EXAMPLE EXAMPLE EXAMPLE EXAMPLE COMPARATIVE COMPARATIVE1 2 3 4 5 EXAMPLE 1 EXAMPLE 2 VN FILM HEATER SETTING 485 485 485 520 550485 485 FOR- TEMPERATURE (° C.) MATION PRESSURE (Pa) 58 58 58 58 58 5858 CON- H₂ FLOW RATE (ml/min) 200 200 200 200 200 200 200 DITIONS N₂FLOW RATE (ml/min) 50 50 50 50 50 50 50 VCl₄ FLOW RATE (sccm) 5.1 4.84.7 4.7 4.7 3.1 4.1 Ar FLOW RATE (ml/min) 5 5 5 5 5 5 5 VOLTAGE OF PULSE1500 1500 1500 1500 1500 1500 1500 POWER SUPPLY (V) FREQUENCY OF PULSE25 25 25 25 25 25 25 POWER SUPPLY (kHz) DUTY RATIO (%) 30 30 30 30 30 3030 OUTPUT FORM UNIPOLAR UNIPOLAR UNIPOLAR UNIPOLAR UNIPOLAR UNIPOLARUNIPOLAR PROCESSING TIME (min) 180 180 180 180 180 180 360

<Hardness Measurement of Vanadium Nitride Film>

On each of the test pieces obtained by the above film formationprocessing, hardness measurement is performed. The hardness measurementis performed by the nano-indentation method using FISCHER SCOPE(registered trademark) HM42000 manufactured by Fischer Instruments.Specifically, a Vickers indenter is pushed into each test piece with amaximum indentation load set to 10 mN, and an indentation depth iscontinuously measured. Based on the change in indentation depth, theMartens hardness, and the Vickers hardness converted from the Martenshardness, and the complex elastic modulus are calculated by a measuringdevice. The calculated Vickers hardness is displayed on a screen of themeasuring device, and the numerical value is used as the hardness of thevanadium nitride film at a measurement point. In this example, theVickers hardnesses at arbitrary 20 points on the surface of the testpiece are obtained, and an average value of the obtained hardnesses isrecorded as the hardness of the vanadium nitride film.

Note that in pushing the indenter into the test piece, an indentationload propagates to a depth of about 10 times the maximum indentationdepth of the indenter in some cases. Therefore, once the propagation ofthe indentation load reaches the base material of the test piece, theinfluence of the base material may be included in the result of thehardness measurement. Accordingly, for measuring the real hardness ofthe vanadium nitride film, it is necessary to satisfy “the filmthickness of the vanadium nitride film > the maximum indentation depthof the indenter×10”.

<Film Thickness Measurement>

Hence, whether the influence of the base material is included in themeasured hardness of the vanadium nitride film is evaluated also in thisexample. The film thickness of the vanadium nitride film is measured byvertically cutting the test piece and subjecting the cut surface tomirror polishing, then observing the cut surface under a metallurgicalmicroscope set at 1000-fold magnification, and performing calculationbased on the observed image information.

<Composition Analysis of Vanadium Nitride Film>

Next, the composition of the vanadium nitride film of each test piecewas analyzed. The analysis conditions are as follows.

EPMA: JXA-8530F manufactured by JEOL Ltd.

Measurement mode: semiquantitative analysis

Acceleration voltage: 15 kV

Irradiation current: 1.0×10⁻⁷ A

Beam shape: spot

Beam diameter set value: 0

Dispersive crystal: LDE6H, TAP, LDE5H, PETH, LIFE, LDE1H

<Measurement Result>

The Vickers hardness, the complex elastic modulus, the film thicknessand the composition of the vanadium nitride film measured in the aboveprocedure are listed in following Table 3.

TABLE 3 COMPARATIVE COMPARATIVE EXAMPLE 1 EXAMPLE 2 EXAMPLE 3 EXAMPLE 4EXAMPLE 5 EXAMPLE 1 EXAMPLE 2 HARDNESS 2989 2541 2525 3004 2642 778 1758OF VN FILM (HV) COMPLEX 277 327 325 328 383 219 301 ELASTIC MODULUS OFVN FILM (GPa) FILM THICKNESS 3.24 3.07 3.18 3.67 3.49 3.39 5.52 OF VNFILM (μm) MAXIMUM 0.164 0.142 0.140 0.119 0.123 0.262 0.173 INDENTATIONDEPTH AT HARDNESS MEASUREMENT (μm) COMPOSITION V (at %) 55.6 51.6 50.162.2 63.2 46.7 48.7 OF VN FILM N (at %) 40.7 43.9 45.3 34.0 33.1 48.447.2 Cl (at %) 2.2 2.7 3.1 2.1 1.8 2.7 2.6 VN FILM 1.37 1.18 1.11 1.831.90 0.96 1.03 CONCENTRATION RATIO (V/N)

As listed in Table 3, the test pieces in Examples 1 to 5 have a hardnessof exceeding HV 2500. In other words, according to the presentinvention, a film harder than the vanadium nitride film having ahardness of about HV 2300 as in the prior art can be obtained. Further,as listed in Table 3, the vanadium nitride film contains larger amountsof vanadium and nitrogen as main elements in the film and contains anext larger amount of chlorine. Here focusing attention on the VNconcentration ratio (V [at %]/N [at %]) in the film, the values of theVN concentration ratio of Examples 1 to 5 are generally larger than thevalues of the VN concentration ratio of Comparative Examples. Takingthis result and the result of hardness measurement of the vanadiumnitride film into consideration, it is found that when the VNconcentration ratio is a fixed value or more, the hardness of thevanadium nitride film improves. More specifically, when the VNconcentration ratio of the vanadium nitride film is 1.08 or more, thevanadium nitride film of an HV 2400 or more which cannot be achieved bythe conventional method can be obtained.

Further, the test pieces in Examples 1 to 5 have excellentcharacteristics such as a complex elastic modulus of the vanadiumnitride film of 400 GPa or less. In particular, focusing attention onExamples 1 and Example 2, the vanadium nitride film in Example 1decreases in complex elastic modulus though its hardness increases withrespect to the vanadium nitride film in Example 2. More specifically,the vanadium nitride film in Example 1 is harder and has a widerelastically deformed region than the vanadium nitride film in Example 2and thereby greatly improves in abrasion resistance. Besides, focusingattention on Example 4 and Example 5, the vanadium nitride film inExample 4 decreases in complex elastic modulus though its hardnessincreases with respect to the vanadium nitride film in Example 5. Morespecifically; the vanadium nitride film in Example 4 is harder and has awider elastically deformed region than the vanadium nitride film inExample 5 and thereby greatly improves in abrasion resistance.

According to the results of the above examples, it is found that whenthe VN concentration ratio is 1.08 or more, the hardness can beincreased to improve the abrasion resistance. For increasing thehardness and decreasing the complex elastic modulus to further improvethe abrasion resistance, the VN concentration ratio is preferably 1.30to 1.85.

Note that the thickness of the vanadium nitride film of each test pieceis a thickness greatly exceeding 10 times the maximum indentation depthof the indenter at the hardness measurement as listed in Table 3, andtherefore it can be said that the hardness of the vanadium nitride filmlisted in Table 3 is a numerical value not influenced by the basematerial. Further, as is found from the cross-sectional image of thetest piece in Example 1 illustrated in FIG. 4, the vanadium nitride filmis uniformly formed on the entire surface of the base material, so thatit is estimated that the film thickness at an arbitrary point of thetest piece becomes almost equivalent value to the film thicknessmeasurement result listed in Table 3. Therefore, it is found that themeasurement result at a part that receives influence of the hardness ofthe base material is not included in the measurement results of thehardnesses at arbitrary 20 points. In short, the hardness of thevanadium nitride film listed in Table 3 is the hardness of the filmitself

Note that when the film thickness of the vanadium nitride film to beformed on the surface of the base material is 1 μm or less, themeasurement result of EPMA includes the influence of the composition ofcomponents of the base material. Therefore, in the case of calculatingthe VN concentration ratio of a vanadium nitride film having a smallfilm thickness, it is necessary to perform EPMA measurement of only thebase material in advance and subtract the vanadium concentration and thenitrogen concentration derived from the base material from themeasurement result of EPMA after the film formation of the vanadiumnitride film.

INDUSTRIAL APPLICABILITY

The present invention is applicable to hard coating treatment of a die,a tool and so on.

EXPLANATION OF CODES

-   -   1 member coated with a vanadium nitride film    -   2 base material    -   3 vanadium nitride film    -   4 buffer film    -   5 concentration gradient film    -   10 plasma processing apparatus    -   11 chamber    -   12 anode    -   13 cathode    -   14 pulse power supply    -   15 gas supply pipe    -   16 gas exhaust pipe

1. A method for manufacturing a member coated with a vanadium nitridefilm, the method comprising: supplying a raw material gas containing anitrogen source gas, a vanadium chloride gas, and a hydrogen gas informing the vanadium nitride film on a surface of a base material; andforming a vanadium nitride film having a ratio V [at %]/N [at %] betweena vanadium element concentration and a nitrogen element concentration of1.08 or more and a chlorine element concentration of 1 at % or more and5 at % or less on the surface of the base material by a plasma chemicalvapor deposition method; wherein a total of the vanadium elementconcentration and the nitrogen element concentration in the vanadiumnitride film is 90 at % or more.
 2. The method for manufacturing amember coated with a vanadium nitride film according to claim 1, whereinthe vanadium element concentration in the vanadium nitride film is 49.5at % or more.
 3. The method for manufacturing a member coated with avanadium nitride film according to claim 1, wherein the vanadiumchloride gas is a vanadium tetrachloride gas.